The use of a camera, typically with a low resolution, for scanning documents is known. This involves the camera and/or the mobile telephone being moved over the document at a short distance from it. A final image is generated from the images and/or partial images recorded in this way.
The images are typically recorded using a high scanning frequency of 15 or 30 Hertz. Accordingly, this contributes to adjacent images having an extremely high image overlap. A high resolution final image can be continuously established by adjoining narrow film strips from the respective image center and allowing for the camera displacement.
Small variations in the distance between the camera and the document and a slight tilting of the camera which occurs with a hand-held camera nevertheless result in extremely troublesome changes in size in the document content displayed. The size changes must be adjusted to each other in a first processing step, so that the high resolution final image can be constructed without errors. The determination of the position of the camera sensor with respect to the document, particularly in terms of the distance and tilting, is an important condition for fault compensation. The calculation of the relative position information from successive images is a known approach, which is extremely complex and provides results which are mostly very unstable. In general, tiltings of the camera in relation to the document can only be determined with great difficulty, on the basis of the recorded image information by means of image processing.